Transistor ignition system



Oct. 6, 1964 s. B. ROBBINS 3,152,231

TRANSISTOR IGNITION SYSTEM Filed June 25, 1962 2 Sheets-Sheet l INVENT OR. SAMUEL B. ROBE/N5 BY CAP: 2 I

A TTORNE Y Oct. 6, 1964 s. B. ROBBINS 3,152,281

TRANSISTOR IGNITION SYSTEM Filed June 25, 1962 2 Sheets-Sh et 2 l36 04 mo i I O /00 f Hu k INVENT OR. SAMUEL B. ROBE/NS A TTOR/VEV United States Patent 3,152,281 TRANSISTOR TGNITIGN SYSTEM Samuel B. Robbins, Rochester, Mich, assignor to General Motors Corporation, Detroit, Mich, a corporation of Delaware Filed June 25, 1%2, Ser. No. 2494,736 8 Claims. (Cl. 315201) This invention relates to ignition systems for internal combustion engines and more particularly to ignition systems wherein one or more transistors control the current flow to the primary winding of the ignition coil.

One of the objects of this invention is to provide an ignition system wherein a semiconductor such as a transistor controls the current flow through the primary winding of an ignition coil in timed relation with operation of the engine and wherein means are provided for preventing the destruction of the transistor or transistors by the kick back voltage of the primary winding.

A more specific object of this invention is to provide a transistor ignition system wherein a diode is connected in series with the transistor to prevent the kick back voltage of the primary winding from forcing a destructive current through the transistor or transistors and wherein this diode is connected in series with a buffer resistor and in parallel with another resistor which provides a current path for current developed by the kick back voltage.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein preferred embodiments of the present invention are clearly shown.

In the drawings:

FTGURE l is a schematic circuit diagram of an ignition system made in accordance with this invention.

FIGURE 2 is a top view of a magnetic pickup assembly which is shown schematically in FIGURE 1.

FIGURE 3 is a sectional view taken along line 3-3 of FIGURE 2.

FIGURE 4 is a schematic diagram of a modified ignition system made in accordance with this invention and using breaker cont acts to control the conductivity of the transistors.

Referring now to the drawings and more particularly to FIGURE 1, the reference numeral 19 designates an internal combustion engine which has a plurality of spark plugs 12. There are eight spark plugs shown for use with an eight cylinder engine but it is apparent to those skilled in the art that the number of spark plugs may be varied according to the number of engine cylinders. One side of all of the spark plugs is grounded as is shown in FIGURE 1 whereas the opposite side of the spark plugs is connected with electrodes 14 of a conventional distributor 16. This distributor includes the usual rotor 18 conected with lead wire 24 and this rotor as is well known to those skilled in the art passes in close proximity to the electrodes 14 to distribute the firing power to the spark plugs 12 as the rotor 18 rotates.

The lead wire 29 is connected with the secondary winding 22 of an ignition coil which is generally designated by reference numeral 24. The ignition coil has a primary winding 26 one side of which is connected with the lead wire 28 and the opposite side of which is grounded via lead wire 29. It is seen that one side of the secondary winding 22 is also grounded.

The current flow through the primary winding 26 of the ignition coil is controlled by a pair of PNP transistors Sil and 32 which are connected in series as shown. Thus, the collector electrode of transistor 32 is connected with the emitter electrode of transistor 30. The collector electrode of transistor 39 is connected with junction 34 on the lead wire 28 via a diode 36 and a resistor 38. The base electrode of transistor 3i) is connected with junction 39 through a resistor 45? and a diode 41. The emitter and base electrodes of transistor 3% are connected by a resistor 42.

The base electrode of transistor 32 is connected with junction 39 via the resistor 43. The emitter electrode of transistor 32 is connected with junction 44 and it is seen that a resistor 46 connects the junctions 34 and 44. The emitter and base electrodes of transistor 32 are connected by a resistor 48.

The junction 39 is connected with the emitter electrode of a PNP transistor 5. The collector electrode of tran sistor Sll is connected to ground and is also connected with junction 52. The base electrode of transistor 56 is connected with junction 54 and with the emitter electrode of another PNP transistor 56. It is seen that the collector electrode of transistor 56 is connected with junction 52 and is therefore grounded.

The junction 54 is connected with a junction 58 via a resistor 6i). The base electrode of transistor 56 is connected with junction 62 and is connected with junction 64 through a thermistor 66.

The junction 58 is connected in series with a ballast resistor 63 which in turn is connected in series with an ignition switch 79. The ignition switch 74? s connected in series with a battery 72, one side of which is grounded.

The ignition system of this invention is controlled as to timing by a magnetic pick up device which is generally designated by reference numeral 74. This magnetic pick up device includes a magnetic core 76 upon which is wound the coil winding 78. As can be seen from FIG- URES 2 and 3, the core 76 and the coil winding 78 are supported in a housing 84) which is preferably formed of a nonmagnetic material. The housing 8% supports a shaft 82 which carries a rotor member 84 formed of a nonmagnetic material. The rotor 84 carries eight permanent magnets 86 which can swing between the legs 88 and 99 of the magnetic core 76. The shaft S2 is driven by the engine it) and as the rotor 34 rotates and the permanent magnets pass between the legs 88 and 94) of the core, a series of voltage pulses are induced in the coil winding 78. There will be eight pulses of voltage induced in the coil winding 78 for each revolution of the rotor 84. It will, of course, be appreciated that the number of permanent magnets carried by the rotor will correspond to the number of cylinders of the engine It and can be varied accordingly.

\Vhen it is desired to energize the ignition system of FIGURE 1, the ignition switch 70 is closed. The rotor 84 is then rotated when the engine is cranked or when the engine is running to cause a series of voltage pulses to be induced in the coil winding 73.

When transistor as is conducting in its emitter-collector circuit, the potential of junction 54 will approach ground potential since there is very little or no voltage drop in the emitter-collector circuit of transistor 56. When junction 54 moves toward ground potential, the transistor 56 is turned on in its emitter to collector circuit. With transistor 5% turned on in its emitter to collector circuit, a base circuit for transistors 36 and 32 is completed through the emitter to collector circuit of transistor 50. When transistors 30 and 32 have a complete base circuit through transistor 56, they become conductive in their emittercollector circuits so that current can then flow through the primary winding 26 of the ignition coil. This circuit can be traced from the positive side of the battery 72, through the closed ignition switch 7t), through the ballast resistor 6%, through junction 44, through the emitter to collector circuit of transistor 32, through the emitter to collector circuit of transistor 39, through diode 35, through r) resistor 38 and then through the primary winding 26 of the ignition coil to ground.

When one of the permanent magnets 86 swings between the legs ?8 and hi) of the magnetic core '76, a voltage pulse is induced in the coil winding '78 which is of such a polarity as to drive the base electrode of transistor 56 negative an amount sur'iicient to turn on the transistor 56 in its emitter to collector circuit. This turns on the base circuit path for transistor 56 causing it to conduct which in turn causes transistors 30 and 32 to conduct. When transistors 39 and 32 turn on, the circuit to the primary winding 25 is substantially completed and a current flows through the primary winding 26. As the magnet 86 swings out from between the legs 83 and 0, a large electromotive force assisting the voltage is fed across resistor 46 to the base of transistor se, cutting th transistor 56 ofi which in turn causes transistors 319 and 32 to cut off. When transistors 36 and 32 turn off, the circuit to the primary winding 26 is substantially opened and a large voltage is induced in the secondary winding 22. This will cause one of the spark plugs 12 to be fired through the rotor contact 18 and one of the electrodes 14.

It is pointed out that the rotor contact 13 and the rotor 84 rotate in synchronism and that as they rotate, the transistors 3t and 32 are turned on and off in timed relationship with operation of the engine to cause a proper firing of the spark plugs 12.

The diode 36 in combination with the resistors 38 and 46 serves to prevent current flow through the transistors 34 and 32 due to the kick back voltage developed in the primary winding 26. The diode 36 is a semiconductor diode and requires a short amount of time in going from its forward conduction state to its blocking state in order to fully block the current developed by an inverse voltage. The resistor 33 which may be, for example, .2 ohm serves as a buffer resistor to provide a short time delay required for the diode to fully recover or in other words, to give the diode suflicient time to change from its forward conducting state to its blocking state. When the diode 36 blocks the reverse voltage developed in the primary winding 26, any current resulting from this voltage can pass through the resistor 46 and the battery without harming the transistors 39 and 32. The resistor 46 may be a 270 ohm resistor by way of example but not by way of limitation in a 12 volt system. The diode 41 serves to isolate the base electrodes of the transistors 30 and 32.

Referring now more particularly to FIGURE 4, the turning on and off of the transistors is controlled by a pair or" breaker contacts opened and closed in synchronism with operation of the engine rather than by a magnetic pick up assembly of the type shown in FIGURES 2 and 3.

In FIGURE 4, the engine is designated by reference numeral 92 and has eight spark plugs 94-. One side of the spark plugs is grounded and the opposite side of the spark plugs are connected with the electrodes of a distributor generally designated by reference numeral 96. The distributor includes the usual rotor contact 98 driven in synchronism with the engine 2 and in synchronism with a breaker earn 191 The breaker cam 1th) causes an opening and closing of the breaker contacts 102, one of which is grounded and the other of which is connected through the breaker arm to a lead wire 1114.

The system of FIGURE 4 includes a pair of PNP transistors 106 and 1113. The collector electrode of transistor 106 is connected with the emitter electrode of transistor 108. A resistor 110 connects the emitter and base elecrodes of transistor 1%. The collector electrode of transistor 108 is connected with the primary winding 114 of an ignition coil 116 through a diode 118 and a resistor 120. It will be appreciated that the diode 118 and the resistor 121) are equivalent circuit elements to the diode 36 and resistor 38 shown in FIGURE 1. In this connection, it is noted that a resistor 122. is connected between junctions 124 and 126 and performs the same function as resistor 46 in FIGURE 1.

The emitter electrode of transistor 1% is connected with the junction 126 which in turn is connected with lead wire 128. A resistor 13%) connects the lead wire 128 to one side of an ignition switch 132. The opposite side or" the ignition switch is connected to one side of a battery 134 the opposite side of the battery being grounded as shown.

The base electrode of transistor 1% is connected with a junction 136 through resistor 133. The base electrode of transistor 1% is connected with junction 136 through resistor 14% and a diode 142. It will be appreciated that the diode 142 performs the same function as the diode 41 shown in FIGURE 1.

The secondary winding 117 of the ignition transformer 116 has one side thereof grounded and has an opposite side connected with the rotor contact 98 via the lead wire 144.

The system of FIGURE 4 operates in a fashion similar to that of the system shown in FIGURE 1 with the exception that the turning on and turning oli of the transistors 11% and 168 is controlled by the breaker contacts 1112 rather than by a magnetic pick up. When ignition switch 132 is closed and the breaker contacts 1112 are closed, a base current path can be traced for the transistors which is through the lead wire 194 and through the closed breaker contacts to ground. With the breaker contacts closed, the emitter to collector circuits of transistor 1116 and 1418 are conductive so that current flows from one side of the battery 134, through ignition switch 132, through resistor 13%, through lead wire 128, through the series connected transistors 1116 and 1%, through diode 118, through resistor 129 and then through the primary winding 114 to ground. When the breaker contacts 192 open, the base circuit for the transistors 1% and 1118 is opened so that these series connected transistors become substantially fully nonconductive in their emitter-collector circuits. This substantially reduces the current flow through the primary winding 114 and causes a large voltage to be induced in the secondary winding 117 which is applied to one of the spark plugs 94 to cause one of the spark plugs to fire.

From the foregoing, it can be seen that when the breaker contacts 102 are closed, the transistors 1G6 and 108 are conductive to provide a current path for current flowing through the primary winding 114. When the breaker contacts 162 open, the transistors 1116 and 1118 become nonconductive to break the circuit to the primary winding 114. it will, of course, be appreciated that the opening and closing of the breaker contacts 102 is synchronized with the rotation of rotor contact 98 so that the breaker contacts 19 open when the rotor contact 98 is in alignment with one of the electrodes that is connected to one of the spark plugs 94.

While the embodiments of the present invention as 1 herein disclosed, constitute a preferred form, it is to be primary winding and a secondary winding, means conmeeting said secondary winding with said spark plug, a source of direct current power, at least one transistor having emitter, collector and base electrodes, an energizing circuit for the primary winding of said ignition coil including the emitter-collector circuit of said transistor and a series connected diode and a first resistor, a second resistor connected between one side of said power source and the primary winding of said ignition coil bypassing the emitter-collector circuit of said transistor and said series connected first resistor and diode, and control means connected with the base electrode of said transistor for controlling its conductivity in its emitter-collector circuit in timed relationship with operation of said engine.

2. The system according to claim 1 wherein the control means is a magnetic pick-up device.

3. The system according to claim 1 wherein the control means comprises a pair of breaker contacts opened and closed in synchronism with operation of said engine.

4. An ignition system for an internal combustion engine comprising, a spark plug for said engine, an ignition coil having a primary winding and a secondary winding, means connecting said secondary winding with said spark plug, a three terminal semiconductor switch means, a circuit connecting a first terminal of said semiconductor switch means with one side of the primary winding of said ignition coil including a diode and a buffer resistor, a source of direct current power, a circuit connecting a second terminal of said semiconductor switch means with one side of said source of direct current power, a second resistor having a higher resistance value than said buffer resistor connecting one side of said power source with one side of said primary Winding and bypassing the circuit including said diode and said bufier resistor, and control means driven by said engine connected with the third terminal of said semiconductor switch means for controlling the turning on and turning off of said semiconductor switch means in synchronism with operation of said engine.

5. The ignition system according to claim 4 wherein the control means includes a voltage pulse generating means driven in synchronism with the engine.

6. The ignition system according to claim 4 wherein the control means includes breaker contacts opened and closed in synchronism with operation of said engine.

7. An ignition system for an internal combustion engine comprising, a spark plug, an ignition coil having a primary winding and a secondary winding, means connecting said secondary winding with said spark plug, a source of direct current voltage, a first transistor having emitter, collector and base electrodes, a circuit connecting one side of said voltage source with one side of said primary winding including the emitter-collector circuit of said transistor, a diode and a bufier resistor, a second resistor having a higher resistance value than said bufier resistor bypassing the emitter-collector circuit of said first transistor and said diode and bufier resistor, a second transistor having emitter, collector and base electrodes, a third transistor having emitter, collector and base electrodes, means connecting the emitter electrode of said second transistor with the base electrode of said first transistor, means connecting the emitter electrode of said third transistor with the base electrode of said second transistor, a magnetic pick up device including a rotor and a coil winding, said coil winding having voltage pulses induced therein as said rotor rotates, means connecting said rotor with said engine to be driven thereby, and means connecting said coil winding with the base electrode of said third transistor.

8. The system according to claim 7 wherein a thermistor is connected between the base electrode of said third transistor and one side of said voltage source.

References Cited in the file of this patent UNITED STATES PATENTS 2,884,545 Houck Apr. 28, 1959 2,898,392 Jaeschke Aug. 4, 1959 2,955,248 Short Oct. 4, 1960 

1. AN IGNITION SYSTEM FOR AN INTERNAL COMBUSTION ENGINE COMPRISING A SPARK PLUG, AN IGNITION COIL HAVING A PRIMARY WINDING AND A SECONDARY WINDING, MEANS CONNECTING SAID SECONDARY WINDING WITH SAID SPARK PLUG, A SOURCE OF DIRECT CURRENT POWER, AT LEAST ONE TRANSISTOR HAVING EMITTER, COLLECTOR AND BASE ELECTRODES, AN ENERGIZING CIRCUIT FOR THE PRIMARY WINDING OF SAID IGNITION COIL INCLUDING THE EMITTER-COLLECTOR CUIRCUIT OF SAID TRANSISTOR AND A SERIES CONNECTED DIODE AND A FIRST RESISTOR, A SECOND RESISTOR CONNECTED BETWEEN ONE SIDE OF SAID POWER SOURCE AND THE PRIMARY WINDING OF SAID IGNITION COIL BYPASSING 